1. Field
The presently disclosed subject matter relates to a non-spectacled stereoscopic display apparatus.
2. Description of the Related Art
Generally, a stereoscopic display apparatus provides parallax images from viewpoints of both eyes of an observer. The stereoscopic display apparatus is classified into the spectacled type and the non-spectacled type. The spectacled type stereoscopic display apparatus need specific glasses, while the non-spectacled type stereoscopic display apparatus needs no specific glasses.
As illustrated in FIG. 25, which illustrates a prior art non-spectacled stereoscopic display apparatus (see: JP2010-262198A), this non-spectacled stereoscopic display apparatus is constructed by a light guide plate 1 with a light distributing face Sd and a light emitting face Sout1, two light sources 2a and 2b disposed on light incident faces Sina and Sinb of the light guide plate 1, a single-face-deformed triangular prism sheet 3 disposed on the light emitting face Sout1 of the light guide plate 1, a transmissive liquid crystal display panel 4 disposed on a light emitting face Sout3 of the single-face-deformed triangular prism sheet 3, and a synchronous drive circuit 5 for synchronizing the light sources 2a and 2b to display parallax images on the transmissive liquid crystal display panel 4. When one of the light sources 2a and 2b is turned ON, the single-face-deformed triangular prism sheet 3 is configured to emit light to one eye of the observer with no emission of light to the other eye. Also, provided on the light incident and light emission sides, respectively, of the transmissive liquid crystal display panel 4 are polarizing plates 4a and 4b. An air gap 6 is present between the single-face-deformed triangular prism sheet 3 and the transmissive liquid crystal display panel 4. Thus, a stereoscopic image with the same number of pixels as that of the transmissive liquid crystal display panel 4 can be displayed.
In FIG. 25, two light guide plates, i.e., a lower light guide plate and an upper light guide plate superposed onto the lower light guide plate can be provided instead of the light guide plate 1 (see: JP2010-286813A).
In FIG. 25, the light guide plate 1, the light sources 2a and 2b, and the single-face-deformed triangular prism sheet 3 can entirely be called a three-dimensional (3D) backlight source BS.
In the non-spectacled stereoscopic display apparatus of FIG. 25, however, since anisotropy of polarization of the emitted light from the light emitting face Sout3 of the 3D backlight source BS is not determined, the polarization of the emitted light does not always coincide with the polarizing axis of the polarizing plate 4a, so that the optical characteristics of the stereoscopic display apparatus of FIG. 25 would deteriorate.
Also, in the non-spectacled stereoscopic display apparatus of FIG. 25, as illustrated in FIG. 26, since the air gap 6 is present between the 3D backlight source BS and the transmissive liquid crystal display panel 4, light L1 for the left eye side may be emitted at an angle of less than 15° from the transmissive liquid crystal display panel 4; however, other light L2 for the left eye side may be totally reflected at the light emitting face Sout3 of the single-face deformed triangular prism sheet 3 due to the difference Δn=0.57 in refractive index n between the single-face-deformed triangular prism sheet 3 with n=1.57 and the air gap 6 with n=1.0, so that the light L2 would be stray light SL whose part is returned to the light guide plate 1 and emitted at an angle of −4° from the transmissive liquid crystal display panel 4 through the single-face-deformed triangular prism sheet 3 as a crosstalk for the right eye side, thus hindering a stereoscopic display.
Note that JP2002-090717A makes an angle between a ridegeline (talweg) of a light guide plate and a polarizing axis of a polarizing plate of a liquid crystal panel almost zero, or less than 45°, thereby increasing the luminous intensity. Also, JP2010-286700A discloses a polarizing plate including a polarizing film and a triangular prism sheet which are combined by an adhesive layer with no air gap, thereby increasing the luminous intensity.